Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.90	8.155%	$111.2915	$111.29	$111.30	$111.30
Purchase #2	$136.60	4.441%	$142.6664	$142.67	$142.65	$142.70
Purchase #3	$208.31	6.376%	$221.5918	$221.59	$221.60	$221.60
Purchase #4	$16.69	8.594%	$18.1243	$18.12	$18.10	$18.10
Purchase #5	$174.45	6.123%	$185.1316	$185.13	$185.15	$185.10
Purchase #6	$145.70	5.649%	$153.9306	$153.93	$153.95	$153.90
Purchase #7	$40.62	9.645%	$44.5378	$44.54	$44.55	$44.50
7 purchase totals =	$825.27		$877.2740	$877.27	$877.30	$877.20